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Text: Riëtte Steinberg Registered Dietitian (SA) PVMNutritional Sciences (Proteins. Vitamins. Minerals)

Vitamins and minerals are essenti al for many metabolic processes in the body and are important in supporti ng growth and development. They are required for reacti ons involved with physical acti vity and exercise, such as muscle contracti on, energy expenditure, carbohydrate, protein and fat metabolism, oxygen transfer and delivery as well as ti ssue repair. Some vitamins act as anti oxidants, buff ering free radicals produced by increased energy turnover.Many athletes supplement their diet with extra vitamins and minerals, desiring to improve health, enhance recovery, improve sport performance and prevent infecti ous diseases. They have reported the use of B-complex vitamins, vitamin E, iron and especially vitamin C.

But is supplementati on really necessary? Studies have demonstrated an increase in reacti ve oxygen species (ROS) with moderate to high intensity exercise. Energy producti on involves reducti on of oxygen in the mitochondria (energy producing part of the cell), during which some of the oxygen turns into free radicals. Free radicals are unstable, reacti ve and potenti ally harmful substances. Excessive producti on, or failure to protect against free radicals, has been linked to cell and mitochondria membrane damage, decreased

immunity and other adverse health eff ects. Anti oxidants such as vitamin C and E build up a protecti on system against free radical att ack, thus an increased need may arise. Some minerals may be lost through sweat such as magnesium and zinc, while others may be lost in urine. Generally, if energy intake is suffi cient, varied and balanced and the athlete has a healthy nutriti onal status, vitamin and mineral supplementati on is not warranted. Increased requirements are however subject to the intensity, durati on, and frequency of the applicable event/sport. Supplementati on is also dependant on the nutriti onal status of the athlete. Some athletes with a poor nutriti onal status or impaired dietary intake might benefi t from supplementati on. For athletes that restrict energy intake, such as in sports with weight restricti ons or those that limit certain foods/food groups, supplementati on may also be warranted.

Can micronutrient supplements be harmful?Some athletes supplement micronutrients “just in case”. Toxicity however, can arise when daily doses rise above a certain threshold limit. Megadoses of several vitamins may be pathological, parti cularly vitamin A, D, niacin and B6.Natural anti oxidants like vitamin C

and E, caretenoids and polyphenols like fl avonoids have many health benefi ts, including protecti ve eff ects against cardiovascular disease, certain forms of cancer, and photosensiti vity diseases. When supplementi ng with high doses, benefi cial anti oxidants can become harmful pro-oxidants. A pro-oxidant is a compound that induces oxidati ve stress and inhibits anti oxidant systems. Thus, rather than protecti ng against damage, these substances cause damage. The pro-oxidant acti on of anti oxidants includes:

• Vitamin C in high doses causes cell death, and DNA damage

• Vitamin E in high doses causesincreased α-tocopherol radicals which can initi ate lipid peroxidati on (damage to lipid cell membranes)

• Flavanoids in high doses can form radicals instead of scavenging them and also cause lipid peroxidati on

Other than harmful pro-oxidant eff ects, reducti ons in vascular functi on have also been noted with administrati on of mixed anti oxidants. Acute doses of vitamin C and E demonstrated reduced brachial artery vasodilatati on which reduces exercise capacity and performance.

Vitamin C is known to remove free radicals produced by exercise, thereby reducing the potenti al

VITAMINS MINERALS

too much of a good thing?

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Table 1: Adverse effects of some micronutrients:

*Take note: the above mentioned recommendations differ for various age and gender groups.

negative consequences of ROS such as muscle damage, immune dysfunction and fatigue. ROS is not all bad though. Moderate ROS production causes physiological changes such as increases in mitochondrial growth factors and cell survival proteins, reductions in muscle atrophy and proteins involved in cell signaling pathways and amplifications of immune function. Moderate ROS concentrations are further required for optimal training adaptation and muscle function. Supplementation of vitamin C in doses exceeding 1 g/d has been shown to attenuate the exercise derived rise in ROS and blocks cell signaling. Vitamin C in doses of >1g/d thus appear to reduce training induced adaptations by reducing mitochondrial biogenesis or by possible vascular function alteration, and is not recommended.

Toxicity of minerals is relatively rare. The levels associated with toxicity can normally be obtained only through the use of supplements or fortified foods. Intakes needed to reach toxicity levels are high, but when toxic symptoms do appear, they can be fatal. Most multi-vitamin supplements contain minerals close to RDA levels or less, but when athletes self-prescribe, toxicity can become a concern. All trace minerals are toxic when consumed at high doses for a long period of time. Even though toxicity levels are high, certain nutrient interactions can occur with high mineral intake. High intakes of one mineral might interfere with the absorption of another, causing a deficiency. For this reason, precautionary use of mineral supplements should not exceed 5x the recommended intake.

RDA (recommended intake), UL (Upper limit)

Major food sources Major functions in the body Symptoms of excessive consumption

Vitamin A RDA: 900 RAEUL: 3 mg/d

Liver, whole milk, cheese, car-rots, green leafy vegetables, sweet potatoes

Promotes bone develop-ment, night vision, maintain skin & mucous membranes

Nausea, headache, fatigue, liver and spleen damage, skin peeling, joint pain

Vitamin C RDA 90mg/dUL: 2000mg/d

Citrus fruits, green leafy vegetables, broccoli, peppers, strawberries, potatoes

Forms collagen essential for connective tissue develop-ment, aids in iron absorp-tion, antioxidant

Diarrhea, possible kidney stones, re-bound scurvy

Vitamin E RDA: 150mcg/dUL: 1000mg/d

Vegetable oils, margarine, green leafy vegetables, whole grains, egg yolks.

Antioxidant, Headache, fatigue, diarrhea

Vitamin B6 RDA: 1.3mg/dUL: 100mg/d

Liver, lean meats, fish, poultry, legumes, green leafy vegetables, baked potatoes, bananas

Coenzyme in protein metabolism, formation of hemoglobin and red blood cells, needed for glycolysis and gluconeogenesis

Loss of nerve sensation, impaired gait

Vitamin B3 RDA: 16mg/dUL:35mg/d

Lean meat, fish, poultry, whole grains, beans

Coenzyme for aerobic and anaerobic production of energy, fat synthesis, healthy skin

Headache, nausea, burning and itching skin, flushing of the face, liver damage.

Calcium RDA:1000mg/dUL: 2500mg/d

Dairy products, dried beans and peas, dark green leafy vegetables.

Bone formation, enzyme activation , nerve impulse transmission, muscle con-traction

Constipation , inhibition of trace mineral absorption , heart arrhyth-mias, kidney stones

Magnesium RDA: 420mg/dUL: 350mg/d from supplements

Milk and yoghurt, dried beans, nuts, whole grains, fruit and vegetables

Protein synthesis, glucose metabolism , smooth muscle contraction, bone component.

Nausea, vomiting, diarrhea.

Iron RDA: 8mg/dUL: 40mg/d

Liver, meat, fish, poultry, dried beans and peas, whole grains, spinach, broccoli

Hemoglobin and myoglobin formation, electron transfer, oxidative process

Hemochromatosis, liver damage

Zinc RDA: 11mg/d Organ meats, meat, fish, poultry, dairy products, nuts, whole grains, vegetables, spinach, asparagus

Cofactor of many enzymes involved in energy metabo-lism, protein synthesis, im-mune function, sensations of taste, smell

Increased LDL and decreased HDL cholesterol, impaired immune system, nausea, vomiting, impaired copper absorption.

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PVM Nutriti onal Sciences off ers superior nutriti on through applied science. Since 1968 PVM, the producer of the worlds original energy bar, has remained dedicated to a cutti ng edge understanding of the biology of energy exchanges between humans and their environment. PVM is involved with numerous top athletes and sport teams and is also subcontracted to conditi on the Free State Cheetahs.

Alfred Rheeder - PVM Nutriti onal Sciences. Should you require nutriti onal assistance contact PVM at (012) 804 7676 or visit www.pvm.co.za

What intake level is considered safe?

Because more and more foods are being forti fi ed these days, reaching total requirements is not that hard and the risk of over-supplementi ng when taking extra micronutrients is high.

• The upper limit (UL) is the maximum quanti ty of a nutrient most individuals can consume without resultant adverse eff ects.

• It is recommended that any precauti onary use of supplements should remain within the recommended intake ranges.

• Because of increased oxidati ve stress, a “normal dose” of 60-90mg/d vitamin C may not be appropriate for athletes. Reviewers found that a dose of 0.2-1g/d will reduce oxidati ve stress by the needed modest margin. In one study, a dose of 500mg/d vitamin C, did not reduce exercise induced blood fl ow – this dose is thus considered to be safe.

• It is recommended that intake should come from fi ve servings of fruit and vegetables due to other health benefi ts provided by these foods. Fruit and vegetable intake may be associated with lower cancer risk not because of vitamin C alone, but because of the interacti ons with other bioacti ve compounds and phytochemicals.

• Studies support the noti on that vitamin C in isolati on is not enough. During ti mes of acute stress, intakes of >0.2 but less than 1g/d may benefi t athletes (such as acute onset of illness or during training camps).

Because every athlete diff ers, current nutriti onal status, energy and nutrient intake have to be assessed and individual requirements should be determined. A registered dieti ti an with experti se in sport nutriti on should be consulted to establish an athlete’s individual nutriti on and performance goals.

“When talented, moti vated and highly trained athletes meet for competi ti on the margin between victory and defeat is usually small. When everything else is equal, nutriti on can make the diff erence between winning and losing” – Maughan (2002).